Mol Sieve Afterfilters Failure

[EmmanuelTop]

Hi there,

We are in the middle of startup of LNG Train, and yesterday one of our Mol Sieve afterfilters was found collapsed. That forced us to cut back on feed rate so as to avoid breakage of the second (parallel) filter element till we replace cartridges in the first element.

The problem is that we have only 10-micron spares, whereas the original ones are 2-micron size.

Downstream of Mol Sieves is cryogenic plant for NGL recovery, and the feed gas stream enters two plate-fin exchangers equipped with their own (40 Mesh) strainers on the inlet side of both hot/cold streams.

My question is: what is the maximum filter size (micron or Mesh) that can safely be used upstream of plate-fin exchangers and of the turboexpander, and can we use 10-micron elements as spares in this application? I have never seen any exact specification regarding this important item.

Hope to hear some hands-on experience.

Best regards,

http://antwrp.gsfc.nasa.gov/apod/astropix.html

 

[dtlb26]

Sorry, your question is confusing.

If desgined correctly, the 40 mesh strainers are to remove all larger particles. 40 mesh is 420 microns.

I'm confused on why the filter element demads such a small mesh size (ethanol uses a 100 micron size for MSU applications), yet downstream, the micron size for 40 mesh = 420 microns.

Based on your invo..10 micron is fine..can even go higher.

Please post a process flow to ensure I'm understanding u correctly.

 

[EmmanuelTop]

Exactly.

40 Mesh strainer upstream of the plate-fin exchanger is there to remove debris/rust and larger particles, as we are in the commissioning/startup phase. A 10-micron filter upstream of these strainers (and downstream of gas dehydration unit) should remove even smaller particles and fine dust that could plug cryogenic exchangers.

The question is - can we use 10-micron filter element instead of 2-micron, and allow for particles smaller than 10 microns to pass into cryogenic equipment, as they will certainly pass through the 40 Mesh strainers as well.

Sorry for not posting the flow sketch, it is fairly simple: gas filter --> 40 Mesh strainer --> Plate-Fin exchanger, looking from the direction of flow.

http://antwrp.gsfc.nasa.gov/apod/astropix.html